If it is the Cable service, then you must use a Cable Modem provided by them and these days they are supplying a combined Modem and Router in the form of the Superhub. What you can do though is set it in "Modem only" mode and connect your own separate router to it. I have one of these Cable Superhubs and its WiFi performance is not particularly good.

With ADSL via the phone line, you should be able to connect your own combined "Router and ADSL Modem" to the phone line.

Hi,
Thanks for the reply.sorry,it's via cable ,and that's the main reason I would like to change it,poor wi-fi .
I have read about setting up the superhub has a modem ,but would sooner get rid if it completely .i will have another read about the modem option,as I still have my netgear router .
Thanks again